In general, a representative high-speed train system which travels at a speed of 430 km/h or more is a magnetic levitation (maglev) train.
Such maglev train systems include the German normal-conducting attractive-type Transrapid shown in FIG. 1 and the Japanese superconducting repulsive-type MLX Maglev shown in FIG. 2.
The German Transrapid employs a combined levitation propulsion and Linear Synchronous Motor (LSM), and controls a levitation air gap within an error range of ±0.1 mm.
Here, with regard to the supply of onboard power, the German Transrapid and the Japanese MLX receive electricity from a contact-type pantograph while traveling at a low speed of 160 km/h or less or when stopping, contactlessly receive electricity using an induction power supply method during high-speed traveling, and have onboard batteries in order to prepare for an emergency. In particular, the German Transrapid and the Japanese MLX should employ the above power supply method because a large amount of power is required to perform levitation at low speed or while stopping.
Another high-speed train system is a tube railway system in which a closed space called a tube is placed in a near-vacuum and a train travels across the space, and includes a system that is called the Swissmetro shown in FIG. 3.
Still another high-speed train system is a Magneplane system in which a train travels in a semi-circular runway, as shown in FIG. 4.
Meanwhile, recently, U.S. Powell and Danby proposed a maglev train system, as shown in FIG. 5. This system employs quadrupole superconducting magnets to achieve superconducting repulsive levitation and propulsion (using an LSM), thereby achieving the advantage of reducing construction expenses.
Meanwhile, since the above conventional maglev train systems use a method in which a train levitates and travels without using any support, they are subject to the vertical vibrations of a train, so that the air gap between the primary and secondary sides of a linear propulsion motor should be large.
As an example, in the German Transrapid system, when the traveling speed of a train is 450 km/h, the air gap is variably maintained in a range of 8-14 mm within an error range of +0.1 mm depending on the speed. In contrast, when the speed increases to 1,600 km/h or more, a greater air gap is required. Since the system employs a normal-conducting method, efficiency decreases because the magnetic flux density is low, so that the power consumption is high. In this case, the Transrapid employs a combined levitation propulsion and LSM. In order to control the levitation air gap within the error range of ±0.1 mm, the electrical power factor needs to be sacrificed, so that there arises the structural disadvantage of the power consumption increasing because of low electrical efficiency.
Meanwhile, the Japanese MLX system has an air gap in a range of 100-150 mm. From the fact that a rotary motor generally has an air gap in a range of 0.5-1 mm, it can be seen that the efficiency of a linear motor should be poor.
Furthermore, since the conventional maglev trains levitate and then travel using electrical force, they have skids for landing or small-sized emergency wheels and emergency batteries in order to prepare for an unexpected power failure. These emergency landing apparatuses still have many problems and have not been thoroughly certified. In particular, the small-sized emergency wheels do not have a tread profile and a traveling mechanism required by a railway rail-wheel combination, so that the wheels may be damaged or excessive frictional heat may be generated when there is a curve in a landing section. Moreover, in a high-speed region of 600 km/h or more, the skids may be damaged due to excessive frictional heat.
In the case of the Swissmetro, although the tube railway system is normally maintained in a near-vacuum state, the vacuum should be broken in case of an emergency. Since the speed at which the vacuum is broken is almost a sound speed of 1,224 km/h, the train vibrates when such a fast environmental variation occurs. In particular, when a train is vertically vibrated by shock waves while levitating and traveling, movements which threaten safety may be generated and damage in the form of train coils becoming scratched may occur.
Furthermore, since the railroad track structures of the maglev train systems of FIGS. 1 to 3 have a T-shaped railway or a railway having vertical walls, a large space is required in the tube type system and the construction of the facilities thereof requires high expenses, thereby posing the problem of increasing the required cost.
Furthermore, since a turnout for the conventional maglev trains requires that a heavy railroad track itself has to be moved, it is large in size, requires a long turnout time, occupies a large space, requires that the range of a closed tube space should be significantly expanded in the tube railway, and it is not easy to construct a 3 or more railroad track. Accordingly, this is an obstacle to the mass transportation system in which a plurality of vehicles is used and traffic is heavy. Furthermore, since the dispatch of a rescue train in case of an emergency or the passage of a maintenance vehicle is restricted by the complexity of the turnout, there are many difficulties from the point of view of train operation.
Meanwhile, it is difficult to implement a 600 km/h or more high-speed train in a normal open section due to noise and air resistance which increase by the square of the speed of a train in geometric progression when the speed of the train increases.
Furthermore, the adhesive power transmission of the conventional common trains is subject to restraints. Even when these restraints can be overcome, the general steel wheel-type systems still have restraints resulting from the problem of the rapidly increasing wear of rails and the like.